SUPERSTAR 360FM EPROM

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mm3stb
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SUPERSTAR 360FM EPROM

Post by mm3stb » Monday 21st Dec 2009, 11:08

Radio Make and Model: Superstar 360FM
PCB Number: PB010AB
PLL Number: MC145106
Test gear available: Dummy load, frequency counter, digital VOM, analogue VOM
Symptoms: Ch 26 - 40UK missing

What is working: High, Mid, Low band when eprom is turned off

What has been tried: checked and double checked all connections, replaced clear ribbon from ch selector to eprom

Did it suddenly happen ?: N/A
Anything else that may be of help?: as mentioned before it works fine on all bands when eprom is switched off

Hi,
I recently removed the eprom that was fitted to this radio along with sill speaker jack mod. I decided to go for the spectrum communications SC106 http://www.spectrumcomms.co.uk/cbkits.htm#SC106 in kit form. After assembling the kit i proceeded to fit it to the radio. i decided not to fit the trim pot to the clarifier straight away and see if the eprom worked. At the moment the trim pot is still not fitted. It works fine ch1 - 25uk but ch26 - 40uk transmits on 27.851, it does not change.
Can anyone think of anything before i send the eprom back.
Image

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Re: SUPERSTAR 360FM EPROM

Post by zodiac » Monday 21st Dec 2009, 13:14

What was the reason for removing the other Eprom, had it gone faulty.
What I'm getting at is, if one had a fault, or should I say if the radio had a fault before you removed the first Eprom then you need to find that fault first.
You should have checked the radio worked on all channels on all three bands before fitting the new Eprom.
The radio should cover the UK band as well as the other bands without the need to extend the VCO so you can rule that out, unless it's been adjusted too far.
How far is it.
Twice it's length from halfway.

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Re: SUPERSTAR 360FM EPROM

Post by mm3stb » Tuesday 22nd Dec 2009, 4:10

The old eprom was removed because it was going haywire. Transmitting away up on the 10M band
The old eprom was removed a couple of months ago and the radio was working on all channels and on all bands and still does when the eprom is switched off (see 1st post). I checked it with a frequency counter after removing the old eprom and soldering jumpers where the track had been cut. also checked again before fitting eprom and after, providing the switch is in the USA position.

Thanks

Richard

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Re: SUPERSTAR 360FM EPROM

Post by zodiac » Tuesday 22nd Dec 2009, 12:33

The Eprom is not switched on and off it's on all the time, it just changes from one program (set of codes) to another when you flick the switch.
At least you know the wires going to and from the channel switch are wired correct as it works on all three FCC bands, so the fault must be with the Eprom programming for the UK band or the switch wires for the UK band.
Give Spectrum a ring and see what he says.
Dave.
How far is it.
Twice it's length from halfway.

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Re: SUPERSTAR 360FM EPROM

Post by mm3stb » Saturday 16th Jan 2010, 5:14

Just got the EPROM back from spectrum comunications ans he said it checks out fine. I'm at my wits end now, can't work out where i'm going wrong. I've lost track of how many time i have check my connections.

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Re: SUPERSTAR 360FM EPROM

Post by The Defpom » Saturday 16th Jan 2010, 7:53

It could be a badly etched PCB, get a fine knife blade and run it down between every single track on the EPROM PCB, the slightest residue of copper could cause an incorrect input to be seen by the EPROM, you may not even be able to see that the copper is there.

I assume that you have tried adjusting the VCO in case it is running out of lock above CH26UK ?

Also when you assembled the PCB, you did make sure that the resistor array had pin one (marked with a dot usually) at the same end as the voltage regulator ? so the resistor arrays pin 2 should line up with pin 1 of the EPROM.

Double check as well that you installed all four jumpers correctly on the PCB (one link on the top, three bridges underneath).

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Re: SUPERSTAR 360FM EPROM

Post by zodiac » Saturday 16th Jan 2010, 10:52

Scott,
I don't think it's the input lines shorted as it uses the same input codes for all it's bands they don't change.

Richard,
I would agree with the VCO L18 needing a slight adjustment.
Dave.
How far is it.
Twice it's length from halfway.

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Re: SUPERSTAR 360FM EPROM

Post by The Defpom » Saturday 16th Jan 2010, 11:17

I mention the possible bad etching issue as I have come across it myself on one of my own EPROM PCBs, where a program line worked fine until a different band was selected, as the resistive effect of a partial bridge by copper residue from the band selection input dragged a program line voltage off when the line next to it was also at the same level as the band program line. (combined effect of the two lines each side of the problem one), it is very unlikely, but is possible.

I would go with the VCO adjustment first, to rule the easy thing out first.

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Re: SUPERSTAR 360FM EPROM

Post by mm3stb » Wednesday 20th Jan 2010, 1:42

The Defpom wrote: Also when you assembled the PCB, you did make sure that the resistor array had pin one (marked with a dot usually) at the same end as the voltage regulator ? so the resistor arrays pin 2 should line up with pin 1 of the EPROM.

Double check as well that you installed all four jumpers correctly on the PCB (one link on the top, three bridges underneath).
Going by the diagram i thought that pin 1 of the resistor array had to go to pin 1 of the eprom so thats how i had it but i have now moved it back 1 place so now pin 1 of the array is connected to 0v insted of 5v.
I now have a new fault it just stays on one frequency. If i switch between high mid and low the frequency changes but if i change channel it just stays on the same frequency. The kc shidt still works. I'm not sure if i have created this fault or if it's because i have moved the resistor array.
When i probe the connecting from the channel selector and the eprom i get 0v at a few of the wires but nothing on the others, Are the channel codes a mixture of 8v and 0v or is it normal for some to show nothing?
There are 2 wires with 8v and 1 with 0v coming from main pcb and channel selector, the other 6 got to the eprom.


Richard

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Re: SUPERSTAR 360FM EPROM

Post by The Defpom » Wednesday 20th Jan 2010, 4:48

It looks like I steered you wrong there, put the array back where it was, that is what I get from going by memory.

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Re: SUPERSTAR 360FM EPROM

Post by coyote116 » Saturday 23rd Jan 2010, 15:05

Be sure to check electrolitic capacitors in any radio over 15 years old....they dry out and short causing many head aches....have experienced it in the 360FM, President Grant DX, Midland 79-260 ...trust me, it happens with age.

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Re: SUPERSTAR 360FM EPROM

Post by zodiac » Sunday 24th Jan 2010, 13:53

Richard,
Can you give us the voltages at the PLL pins for channels 24, 25 and 26 on the UK band as I've done below, just put a 1 for the pins that are switched on at about 8v.
These are not correct it's just to let you see what I mean.

Dave.
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PLL codes.png
PLL codes.png (2.67 KiB) Viewed 14541 times
How far is it.
Twice it's length from halfway.

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Re: SUPERSTAR 360FM EPROM

Post by mm3stb » Monday 25th Jan 2010, 12:37

I am hoping to have time to have time to work on the radio over the next few days.
Would yo like these reading before returning the resistor array or after?

Thanks for everyones help on this

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Re: SUPERSTAR 360FM EPROM

Post by The Defpom » Monday 25th Jan 2010, 12:44

move the array back first, I was incorrect in thinking it could have been in the wrong holes.

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Re: SUPERSTAR 360FM EPROM

Post by zodiac » Monday 25th Jan 2010, 13:52

Yes put it back as it was as Scott said.
What I'm looking for is to see if the codes for channels 25 and 26 are the same, if they are then it could be IC7 that's faulty, the binary adder MC14008B.
Dave.
How far is it.
Twice it's length from halfway.

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Re: SUPERSTAR 360FM EPROM

Post by coyote116 » Monday 25th Jan 2010, 15:58

Did you check your resistor array to see if one or more burned out internally?

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Re: SUPERSTAR 360FM EPROM

Post by mm3stb » Tuesday 26th Jan 2010, 4:47

Can i just double check that you require the volateges for pins 9 - 17 ? pin 1 being next to the dot then working anti-clockwise

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Re: SUPERSTAR 360FM EPROM

Post by zodiac » Tuesday 26th Jan 2010, 10:59

NO, not on the Eprom board the PLL, that's the MC145106p IC5 on the main PCB in the radio and it's Channels 25,26 and 27 on the UK band not 24,25 and 26 as I said.
Channel 40 of high band is channel 26 of the UK band so you will be able to get all the other three bands but nothing above that if theres a fault with IC 7.
I could be wrong as I haven't got a radio here with that board in to do any testing on.
Please do them from Pins 9 to 17 in that order, you are correct and I gave it you in the wrong order in the above post.
Dave.
How far is it.
Twice it's length from halfway.

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Re: SUPERSTAR 360FM EPROM

Post by mm3stb » Friday 5th Feb 2010, 10:10

Sorry for the delay getting back to you. I have been on decorating duties.
I think you misunderstood me. I was talking about the dot on the PLL. Pin 1 of the PLL being next to the recessed dot.
I have the codes for you

25: O I I O I O I I I
26: O I I O I I O O O
27: O I I O I I O O I

I = +8v

I have also checked the resistor array and all pins read 10k

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Re: SUPERSTAR 360FM EPROM

Post by zodiac » Saturday 6th Feb 2010, 9:44

The codes you have given indicate that things are working as they should right up to the PLL itself and points to the VCO needing slight adjustment as Scott said.
Have you made any adjustment to the VCO ?, even though it had an Eprom in the radio before and shouldn't need adjusting.
Dave.
How far is it.
Twice it's length from halfway.

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Re: SUPERSTAR 360FM EPROM

Post by mm3stb » Sunday 7th Feb 2010, 23:32

Ok so i'll have to give that a try. What was is the best way to remove the wax from the VCO? Wil there be anything else needing adjusted after the VCO?

Thanks for everyones input. Much appreciated!

Richard

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Re: SUPERSTAR 360FM EPROM

Post by The Defpom » Sunday 7th Feb 2010, 23:47

I would actually say to check the voltage at TP2, watch it when you go from CH10 through to CH40 on the UK band, and see if the voltage stops changing once you get to the channels which are not working, the voltage you see is used to control the VCO frequency, and comes from the PLL, it can only produce so much voltage, and then it tops out, it may be about 6V or so, I cannot remember the actual range of that radio.

If the voltage stops changing then adjust the VCO so that the highest channel in the radio does not reach the maximum voltage at TP2 (leave it a little headroom), also check the lowest channels, for the opposite, make sure that they are still working OK too, if you adjust the VCO too far it can stop the lower channels from working (the VCO covers a certain range, adjusting it moves the range up or down).

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Re: SUPERSTAR 360FM EPROM

Post by zodiac » Saturday 13th Feb 2010, 3:03

Richard,
Did you find the problem yet ?.
How far is it.
Twice it's length from halfway.

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Re: SUPERSTAR 360FM EPROM

Post by mm3stb » Saturday 13th Feb 2010, 4:09

Hi,
I haven't had a chance to look at the radio again. I have been on decorating duties. Hoping to have a look at the voltages at TP2 over the next couple of days. Will keep you updated.
If i do have to adjust the VCO what is the best method to remove the wax from the core of the VCO?

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Re: SUPERSTAR 360FM EPROM

Post by The Defpom » Saturday 13th Feb 2010, 9:55

The easiest way is to just pick it out with a small screwdriver, put it to one side, once adjusted, put it back in a remelt it.

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